1. Field of the Invention
The present invention relates to a MIMO communication system, and more particularly, to a MIMO communication system using a pre-coder based on a tight frame to increase an amount of transmitted signals and to improve reception performance, by modulating signals through antenna combination and a pre-coder based on a tight frame and transmitting the modulated signal.
2. Description of the Related Art
Recently, mass contents are actively produced according to development of a next generation mobile terminal and a UHDTV (Ultra-High Definition TV). In addition, consumers who consume mass contents are rapidly increasing.
According to such a trend, mobile communication networks based on LTE (Long Term Evolution) and LTE-A (Advanced) using a bandwidth of 20 to 100 MHz and a MIMO (Multi-Input Multi-Output) technique have come into wide use throughout the world.
A MIMO transmission technique used in LTE and LTE-A having a transmission amount of 500 Mbps to 1 Gbps dramatically increases channel capacity using a number of transmission and reception antennas, and is suitable to transmit mass data.
However, the MIMO transmission technique is vulnerable to interference among channels due to interference among reception signals and complicated receiver algorithm, and it is difficult to embody hardware thereof.
Accordingly, a MIMO transmission technique to which antenna combination is coupled has recently been developed. As the MIMO transmission technique to which the antenna combination is coupled, there are two methods of SSK (Space Shift Keying) and SM (Spatial Modulation).
The SSK uses only combination of antennas which transmit information of many transmission antennas. The SSK technique has an advantage that a receiver is simple and there is no interference among reception signals, but an amount of transmission is small since a signal modulation constellation is not used and signals are transmitted by only transmission antenna combination. In order to complement the disadvantage about the small amount of transmission of the SSK, the SM transmission technique was proposed.
The SM transmission technique is configured to increase an amount of transmission by coupling combination between signal modulation constellations and antennas which transmit signals, and has an advantage that there is no interference among reception signals.
However, in the SM technique, the amount of transmission is smaller than that of the MIMO technique of the existing spatial multiplexing. In addition, since an STBC (Space Time Block Coding)-SM transmission technique capable of improving reception performance of SM through orthogonalization of transmission signals is not good in band efficiency, there is a difficult in coping with increasing mass contents and solving a traffic problem of a mobile communication network.